The present invention relates to a fluid pressure actuated gripper of the type employed in automated workpiece handing devices to clampingly grip and transfer a workpiece from one work station to another at which the workpiece is released from the gripper while a work operation is performed on the workpiece.
Grippers of this type are widely employed and typically take the form of a pneumatic or hydraulic differential pressure motor whose cylinder is fixedly mounted upon the transfer device. At the forward or rod end of the cylinder housing, a gripper jaw mounting structure is fixedly mounted on the cylinder to pivotally support a pair of opposed gripper jaws which are coupled to the piston rod of the motor by a linkage so arranged that upon stroking of the piston rod in one direction the jaws are pivoted to an open position and driven to a closed workpiece gripping position upon stroking of the piston rod in the opposite direction.
In a typical application, the gripper jaws will be closed upon a workpiece near an edge of the workpiece and the gripper will be advanced to position the gripped workpiece in operative relationship with tooling at a work station. The gripper jaws will then be opened to release the workpiece and the transfer device will retract the gripper from the work station while the work operation is performed. At the conclusion of the work operation, the gripper will then be advanced back into the work station and the jaws again closed upon the part to carry the part away from the work station. Opening and closing of the gripper jaws thus takes place when the gripper is in its closest proximity to tooling at the work station. In grippers of the type described above, the gripper jaws pivot about a pivot axis which is stationary during the opening and closing movement, and the path of movement of the jaws between their open and closed position is thus along a circular arc assuming the pivot axis to be horizontal, of constant radius centered at the jaw pivot. Desirably, vertical movement of the jaws between their clamping and release position should be minimized in that vertical separation of the jaws to a position where they are separated from the part is all that is required to release the part, and if this vertical movement is kept at a minimum, problems of vertical clearance will also be minimized. On the other hand, horizontal movement of the jaws relative to a fixed reference point during opening and closing movement may advantageously be relatively large in that this horizontal movement may withdraw the jaws from beneath an overhanging portion of the tooling. Where the jaw is mounted only for movement about a fixed pivot, the horizontal and vertical components of movement of the operative portions of the jaw are established in a fixed and inflexible relationship to each other.
The present invention is especially concerned with the provision of a fluid pressure actuated gripper in which the horizontal component of movement of the gripper jaw during movement between its open and closed positions can be extended or enlarged.